Suppressor for high-frequency



June 8, 1948. A. c. WALL SUPPRESSOR FOR HIGH-FREQUENCY IGNITION SYSTEMS Filed Nov. 21, 1945 INVENTOR- fllexamr 5 ii klL W ATTORNEY Patented June 8, 1948 SUPPRESSOR FOR HIGH-FREQUENCY IGNITION SYSTEMS Alexander 0. Wall, Indianapolis, Ind., assignor to P. It. Mallory & 00., Inc., Indianapolis, Ind., a corporation of Delaware Application November 21, 1945, Serial No. 630,070

11 Claims. 1

This invention relates to ignition systems such as those adapted for use in internal combustion engines and, more particularly, to such a system for producing fuel charge ignition sparks of high frequency and voltage.

It is an object of the invention to disclose a suppressor for such an ignition system to eliminate interference between the successive energizing impulses for the respective spark plug circuits.

Other objects of the invention will be apparent from the following description and accompanying drawings taken in connection with the appended claims.

The invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawings, the scope of the invention being indicated in the appended claims.

In the drawings:

Figure 1 is a schematic circuit diagram showing the suppressor in combination with a high frequency ignition system; and.

Figures 2 and 3 are graphs showing the effect of the suppressor.

In high frequency ignition systems, impulses for exciting the spark plug circuits may be produced by a magneto, the primary winding of which is normally short circuited by a breaker switch. The primary circuit includes a condenser connected across the magneto winding, this primary circuit being shock excited when the breaker switch is opened to provide a train of impulses which are stepped up by the magneto transformer and distributed successively to the separate oscillatory circuits for firing the respective spark plugs. With such a system, the train of impulses initiated by the opening of the breaker switch is oftentimes not sufiiciently damped so as to die away before the next opening of the breaker switch. This results in overlapping of succeeding trains of impulses or interference therebetween which may cause misfiring or faulty operation of the spark plugs. Such faulty operation is particularly serious in aircraft engines which have a relatively large number of cylinders and a comparatively high speed of operation with the result that there is a very short interval between succeeding trains of impulses.

According to this invention, a suppressor is provided for the primary magneto circuit which causes rapid damping of the train of oscillations initiated by the opening of the breaker switch.

In this manner, the energy of the magneto circuits is rapidly dissipated after the first impulse is produced thus substantially eliminating the overlapping of succeeding trains of impulsesor interference therebetween and decreasing the possibility of multiple firing of the spark plug. In a preferred embodiment of the invention, the first impulse of each train is used to shock excite a high frequency oscillatory circuit, the components of which are located within or adjacent the spark plug to be fired. The suppressor, when used with such a circuit, reduces the maximum amplitude of this first impulse and prevents an excessively rapid voltage rise, thus promoting stability of the ignition circuit and improving the low speed operation of the magneto.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the construction of parts without departing from the spirit of the invention. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring now to the drawings in detail, a typical high frequency circuit adapted for use with the suppressor of this invention is shown in Figure 1. This circuit may comprise a magneto [0 having a primary winding H and a secondary winding l2. A condenser I3 and a breaker switch [4 which is operated by a cam l5, are each connected across the primary winding II, one terminal of which may be grounded as at it. When the breaker switch 14 is closed and the magneto I0 is rotated by the engine, a magnetic field is established in the primary winding. The breaker switch periodically opens to shock excite the primary circuit and produce a train of impulses which are stepped up by the magneto and appear across the secondary winding l2. A suppressor S is also connected across the primary winding for a purpose to be hereinafter explained.

The impulses appearing across the secondary winding upon the opening of the breaker switch are distributed successively to a plurality of spark plug exciting circuits by a distributor l! which may comprise a rotatable contactor l8 and a plurality of contacts l9, one for each spark plug circuit. As the latter circuits are similar in structure and operation, only one such circuit will be described. The current from the distributor may pass to an oscillatory circuit 20 through a shielded cable having an inner conductor 22 and a 'of a transformer 39 which may be conveniently-:

grounded outer conductor the latter communicating with a casing 2 3 which, in turn, is connected to the shell 25 of a spark plug unit 25. The components of the oscillatory circuit are mounted within the casing 2t and these compo- 5 nents may include an impulse gap 2'! and a condenser 28 togethertwithqthe primaryrwinding '29 located within the spark plug unit 25. The secondary circuit of the transformer 30 may include a secondary winding 3!, one terminalofavhichjs connected to the shell 25, the other terminal, leading to a contact member 32 which is connected to a spark plug electrode 33. A plurality.of:e1ec-..= trodes 3t may be connected to -the shell .25 to thereby define a gap across which the ignition spark is produced. The constructionrand operation of the aforementioned circuits are describedin my copending application S. N. 549,278,Zen-;i; titled Ignition system and. apparatus thereof.

When a train; oftimpulses-is;producedbyopen ing of the breaker.:'switch: ill; these;- impulses are. stepped upbyathe magnetmlcrand pa s thro h-r distributor -I;l .to'iexcitexthe oscillatory ci fGli i z and thereby energize the,primaryrw nd fi rIn this I manner-,4 a high frequency 50111176111 :iS=iI11uQed=--.-; t in the secondary; windingyztlcwh ch'p duce W: spark :between;. .the .electrodes'a33; 3 4 to ignit a;.-; fuelcharge iii-the adjacent:cylindenltwill be notedlthatathe primary. Winding-:11 and'condenser I. go I 3 comprisean .oscillatoryscircuit with .the result ethat a train of; oscillaticnszafih is :-;produced --vvhen the primary. circuit is shed;- excit d; by o e n t of the breakerswitch; andcthe, .suppressor 'is not connected inthe circuit Alth u h these cs illar; 3;?) tions are somewhatzdamped lthere s atendency for succeeding trains ;of,.; impulses to overlapland interfere .witheach gctherawhich may. cause mis- 3 firingaorfaultyqjoperation; of; the-spark plug Moreover, athe iinitial =ziiolt e ris is 'q e, :r pid- 40. which tends-...to;. cause instability; of: the impulse Q: gap 21 iThese: difficulties: are. eliminatedor; sub- 1 stantially minimized bynthe zsuppressor s which comprises 53a. resistor int and? :saturable reactor 38 connected in-seriesacross the primary;termi nals I I. t will be understood that the resistance 31 may be represented, partially; or: WhO11yi1I:by,. the resistance ofthe reactor 38; :When 'thesuppressor-isnsed, the inductance =38 isunsaturatcd as the voltage builds-up to. the value necessary to: 0 operate oscillatory circuit .ZII and ;.fir.e the :assQ-p. ciated sparlcplugt At this timepthe reactor pr e-.; sents a high impedance acrossthe primary. wind- I ing H and little or-no currentfiows.through the t-i: suppressor.- As the i olta-ge. continues stot build: .5 up, the inductance-38 becomes saturated andthe impedance thereof: is decreasedtto avery small, value with tlie result-that the resistor.- 31. iseffec-ii: 5 tively connected I across the cprimarysmagneto. winding,-this occurring at-the time 1 or shortly. after the voltage builds up to .suiricientvaluafor firin the; spark plu g. .Thereupon;...the energy 10f; the magneto circuits iswrapidly: dissipated: in-;.the resistance, the oscillations produced by-;.the primary winding Il and the condenser.- I Bbeingfrape 4G5 idly damped so that the train of impulses resulting from one-opening of the breakerswitch'does not interfere with-the train of impulses produced I by the next opening c-f the breaken SWitCh;-"-f\; I

A typical voltage curve for the magnetozcircuit'flo embodying :the suppressor S. is indicated at=39 in; Figure 2, this curve showing the waveproduced; y by the magneto circuitsuwithout .taking. vinto .ac: count the effect of: the spark 1 discharge; It will 1 1; be understood thatuthe firstupulseifio is: alonnifi the voltageyvhen the suppressor is .usedw i thecurve-.'5 .I.-shows th .lvoltage wave:whenrno sup-.. pressoris utilizedfllt will be notedthat the,yolt- 1., age rises rapidly ,tothe value. tzne'cessary tocxe cite oscillatory circuit 2i) and fire the associated be furtherlnoted thatthevoltageof curve 59 ap eifective to fire the spark plug after which the oscillations are rapidly damped so that interference between succeeding trains of impulses is eliminated. The rapid damping of the impulses produced by opening of the breaker switch it is also advantageous in preventing burning of the distributor contacts which may be cause d byrthe I relatively undampedosoillationsset up'when no suppressor is used. Furthermore the maximum amplitude or peak voltage of the curve 39 is less thanthat producedvwhen no suppressor is utilized. is, the maximum amplitude 4| of curve 39 is" less than the maximum voltage 42 of the cliryetiifi.ai dzlihci iolt rise is less abrupt.

This has-.lbeentionnd. to be an advanta in i -prov'ing the low-speed .operation of the magneto anduobtaining stable. operation of the impulse gap 21.

. The :efiectiof the spark discharge is shown by the curves of Figure 3. The curve 5i] represents plug. Thereupon, voltagetfallstrapidlyto, a.

1 minimum value 53 aftenwhich a.damped. tr ain.,. of oscillations ispproduced, the oscillations. shown by curvetli being. much. more rapidly damped...

than the oscillations, showniby. curve. 5 I Q :It will proaches the firing Voltage 52 after the spark.

plug has been fired, as indicated at 54. When no.

suppressor is used, the firing voltage may again-t be reachedeafter the. initial firing of lthe sparkv plug, withflthe resultthattwo or morev sparks. may t. be produced Joy-one openingof. the breakerswitch.

jy-rsultfi'n energy losses .andin excessive. r, 0f \the ..circuit components. and, It will be apparent thattthis under. sirable efict is eliminated or greatly ininimizeol,,. ..v

by the use of the suppressor since .thefenergysot the circuit; is rapidly dissipated whereby. the max y imumi voltage produced aiter the firing, as! indiv a. cated at 55, does not approach .the valuenece's, saryto produce a sparkat the plug electrodess The proper values for the resistor. .31 and th I impedance-38 are somewhat critical 3|nd dBp6nds i on the inductance-resistance characteristics-oi the rmagnetopprimaryw Suitable-values of the suppressor components, fora particular Army Navy type ;SFl4 ZN-3 fourteen cylinder aircraft... magneto included a lcohmresistor andasaturable reactor consisting of turns o f #21 wire 3;

upon an El-l5 lamination with fi leaves each;

.025 inch :thick:., These values aregiven purely.

by way-of example, since different types of magnet-csordinarilyrequire different values for the suppressor components and these values: are best determined ernpiricallyawith, the aid of oscilloh,

graphidobservation; w

While-- the present inventiomias to its objects and. advantages-, .h as been described herein as carried; out i in specifie embodiments thereof, it is ample, a: battery; s breaker switch and the primary' of-v a transf0r;mcr mayv be utilized ;for the primary,.ici-rcuit, a condenser and ,the suppressor being shunted across; thebreaker switch. In this case, the respective spark plug circuits may be energized from the secondary winding. Alternatively, a vacuum breaker switch and the suppressor may each be shunted across a generator winding which is coupled directly to the spark plug firing circuits. It is also within the scope of the invention to use coupling transformers in the primary or secondary circuits or to utilize the distributor in the primary circuit in which case a separate breaker switch and suppressor might be provided for each spark plug.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an ignition system, a Winding, means associated with the winding constituting a source of energy for activating an ignition system for energizing a spark plug, and a breaker switch, a condenser, and a suppressor, each connected across said winding, said suppressor including a saturable reactor.

2. In an ignition system, a winding constituting a source of energy for activating an ignition system, means associated with the winding for energizing a spark plug, and a breaker switch, a condenser, and a suppressor, each connected across said winding, said suppressor including a saturable reactor in series with a resistor.

3. In an ignition system, a magneto having primary and secondary windings, means associated with said secondary winding for successively energizing a plurality of spark plug ignition circuits, and a primary circuit for said magneto including a breaker switch, a condenser, a suppressor, each connect-ed across the primary winding of the magneto, said suppressor comprising a saturable reactor in series with a resistor.

4. In an ignition system, a magneto having primary and secondary windings, means for successively energizing a plurality of spark p1ug i nition circuits from said secondary winding, a primary circuit for said magneto, means for periodically exciting said primary circuit to provide a train of impulses for firing a spark plug, and a suppressor comprising a saturable reactor connected in shunt with the primary winding of said magneto, said reactor becoming saturated as the voltage exceeds the value necessary for firing a spark plug whereby the energy in the magneto circuits is rapidly dissipated after the spark plug has been fired.

5. In an ignition system, a magneto having primary and secondary windings, means associated with said secondary winding for successively energizing a plurality of spark plug ignition circuits, and a primary circuit for said magneto including a breaker switch, a condenser, a suppressor, each connected across the primary winding of the magneto, said breaker switch opening periodically to shock excite the primary circuit and provide a train of impulses for firing a spark plug, said suppressor comprising a reactor which becomes saturated as the voltage exceeds the value necessary for firing a spark plug whereby the energy in the magneto circuits is rapidiy dissipated after the spark plug has been fired.

6. In an ignition system, a magneto having primary and secondary windings, means associated with said secondary winding for successively energizing a plurality of spark plug ignition cir cuits, and a breaker switch, a condenser, and a suppressor each connected across said primary winding, said breaker switch opening periodically to shock excite the primary circuit and provide a train of impulses for firing a spark plug, said suppressor comprising a saturable reactor in series with a resistor, the reactor becoming saturated as the voltage exceeds the value necessary for firing a spark plug whereby the resistor is effectively connected across the primary winding to rapidly dissipate the energy in the magneto circuits and prevent interference between the impulses produced by the successive openings of the breaker switch.

7. In an ignition system, a plurality of oscillatory circuits, a spark plug firing circuit coupled to each oscillatory circuit, a magneto having primary and secondary windings, a distributor for successively energizing said oscillatory circuit and the associated firing circuits from said secondary winding, a primary circuit for said magneto, means for periodically exciting said primary circuit to provide a train of impulses for firing a spark plug, and a. suppressor comprising a saturable reactor connected in parallel with the primary circuit of said magneto, said reactor becoming saturated as the voltage exceeds the value necessary for firing a spark plug whereby the energy in the magneto circuits is rapidly dissipated and interference between succeeding trains of impulses is prevented.

8. In a high frequency ignition system, a plurality of oscillatory circuits each comprising an impulse gap, a spark plug firing circuit coupled to each oscillatory circuit, a magneto having primary and secondary windings, a distributor for successively energizing said oscillatory circuits and the associated firing circuits from said secondary winding, and a breaker switch, a condenser, a suppressor, each connected in parallel with said primary winding, said suppressor comprising a saturable reactor in series with a resistor.

9. In a high frequency ignition system, a plurality of oscillatory circuits, a spark plug fining circuit coupled to each oscillatory circuit, a magneto having primary and secondary windings, a distributor for successively energizing said oscillatory circuits and the associated firing circuits from said secondary windings, and a breaker switch, a condenser and a suppressor each connected across said primary winding, said breaker switch opening periodically to shock excite the primary circuit and provide an impulse for firing a spark plug, said suppressor comprising a saturable reactor in series with a resistor, the reactor becoming saturated as the voltage exceeds the value necessary for firing a spark plug whereby the resistor is efiectively connected across the primary windin to rapidly dissipate the energy in the magneto circuits and prevent interference between the impulses produced by the successive openings of the breaker switch,

10. In an ignition system, a winding constituting a source of energy for actuating a spark plug, a circuit including a breaker switch for periodically releasing the energy stored in said winding, and a saturable reactor connected in shunt with said winding, said reactor becoming saturated a short interval after the operation of the breaker switch whereby the energy in said winding is rapidly dissipated in the reactor at the end of said interval.

11. In an ignition system, a winding constituting a source of energy for actuating a spark plug, a circuit including a breaker switch and a condenser for periodically releasing the energy stored in said winding, and a suppressor comprising a saturable reactor connected in series with a resistor, said suppressor being connected in shunt with said winding whereby the reactor REFERENCES CITED 3, 92,

The following:reierencesbare of .record in; the 10 file of this patent: 1i? 

